Write a function `lcs_of_three(X, Y, Z)` that computes the length of the longest common subsequence (LCS) among three given strings `X`, `Y`, and `Z`.
The LCS of three strings is the longest sequence that appears in all three strings in the same order, but not necessarily consecutively.
#### Example Usage
```python [main.nopy]
print(lcs_of_three("AGGT12", "12TXAYB", "12XBA")) # Output: 2
print(lcs_of_three("abcd1e2", "bc12ea", "bd1ea")) # Output: 3
```
#### Constraints
- The input strings can contain any printable characters.
- The function should return an integer representing the length of the LCS.